This invention relates generally to a blood pump and method or use and more specifically to an apparatus and method for providing to a patient a pulsating or counterpulsating blood flow at the proximal end of an aortic line of a cardiopulmonary bypass circuitry.
Developments in surgical techniques has caused cardiopulmonary bypass surgery to become a more widely practiced surgical procedure. During cardiopulmonary bypass surgery the heart is stopped and the blood is taken from the venous system and run through a pump oxygenating system and put back into the aorta, thus bypassing the heart and lungs. Typically this flow is non-pulsatile. Alternatively, roller pumps or centrifugal pumps are utilized to create some sort of rhythmic blood supply. These pumps must be placed at the distal end of the aortic line thereby attenuating any pulse which may have been created, resulting in a somewhat steady flow of blood back to the patient. Establishing a steady flow of blood during coronary bypass has been implicated in fluid accumulation in the lungs and brain and in myocardial strain caused by increased afterload and is therefore undesirable.
Pulsatile blood pumps have been utilized during such operations. The only pulsatile device actually used during surgery was the PAD, a device manufactured by the Datascope Corporation. It was a device placed in the return line to the patient, but not in close proximity to the aortic cannula. Its performance was thus limited. The pulsatile device of U.S. Pat. No. 4,240,409 to Robinson et al was designed as a device for postsurgical use and not during the actual surgery. This type of device is invasive. These types of blood pumps both receive the pulsating blood directly from the blood vessel and must likewise discharge the blood in a pulsating fashion. Sometimes the blood both enters and is discharged through the very same conduit.
Once the patient has undergone cardiopulmonary bypass surgery, patients are normally weaned by decreasing the bypass flow rate and letting the patient's heart assume more and more of the total blood flow. If there is difficulty, pharmacologic support is first employed, if this is unsuccessful, a device called an intraaortic balloon pump is generally used to assist the heart by producing counterpulsation. Counterpulsation is a way to "unload" the heart by lessening the systolic pressure. The balloon pump has been the simplest of all assist devices. The balloon is inserted into the aorta either directly or through the femoral artery. The balloon is collapsed during the ejection of blood from the heart, lowering the aortic pressure and then expanded during the period of filling of the heart to provide diastolic augmentation. This assist device involves additional invasive techniques on a patient that has already been through surgery.
A new apparatus and method to provide pulsatile blood flow that would simulate the patient's own blood pressure and aide in the weaning of patients after cardiopulmonary bypass surgery by providing counterplusatile blood flow will be welcomed in the area of cardiopulmonary bypass surgery. Benefits of such an inovation are decreased catecholamine stress response to cardiopulmonary bypass, reduced fluid overloading resulting from improved renal function and improved postoperative recovery as measured by postoperative tracheal intubation time.